This invention relates to irrigation, and more particularly to an apparatus and method for providing efficient, cost effective, easy to install turf grass irrigation.
Abroad and in the United States a large percentage of potable, fresh water consumption is utilized for the irrigation of landscape turf and other ornamental plantings. The state of the art irrigation systems utilized for delivering this water to turf and landscape plantings are inefficient and contribute greatly to the exhaustion of water reserves in many areas. Sprinkler irrigation systems, which are most commonly used for landscape purposes, lose water to wind drift, evaporation, runoff, and overspray. The tiny spray droplets necessary to achieve uniform water distribution are vulnerable to wind and are more often than not blown out of the area intended to be irrigated, contributing to the overspray problems. Runoff occurs because the spray heads tend to deliver a large amount of water to a large area too quickly for the water to be effectively absorbed into the ground. The ideal application of a sprinkler system is to evenly distribute the water, through the air, to a given area at a rate equivalent or less than the hydraulic loading rate, or water infiltration rate, of the surrounding soil, so that the evenly distributed air born water droplets fall to the ground and are uniformly absorbed into the soil. In addition water droplets from the sprinkler systems tend to impinge on surrounding structures, such as houses, fences, vehicles, etc., causing discoloration, staining and destruction. Despite these limitations, sprinkler irrigation systems easily make up the majority of landscape irrigation systems installed today because of ease of installation and familiarity among irrigation contractors.
Low volume surface drip irrigation devices and lines, typically emitting water in the range of 0.5 to 2 gallons per hour, use an extensive network of conduits with emitters attached to them which are spaced apart on the surface of the area to be irrigated. The water emits from these devices at slow rates and is mainly influenced by capillary action and gravity once it enters the soil area directly around the emission point. Delivery of water in this manner does eliminate overspray and runoff, but is only practical for landscape plantings in areas not subject to traffic or heavy maintenance, and even in those applications, is not practical for dense landscaping with shallow root zones such as ornamental ground covers or turf. If such an irrigation technique were used in traffic areas such as lawns, the lines would have to be laid down 12-18 inches apart and taken up between irrigations to allow for usage of the lawn and regular maintenance. This impracticality, combined with the detracting visual appearance of the lines placed every 12-18 inches along the surface of the lawn make this usage totally unacceptable.
Subsurface drip irrigation systems consist of low volume drip emitter lines, with drip emission rates ranging from 0.5 to 2 gallons per hour, placed beneath the soil surface in order to provide watering of the plants at the roots. The lines consist of extruded polyethylene lines with calibrated emission drip devices either inserted onto or into the line. The water is emitted at the drip rate substantially along the line at points below the soil surface and distributed by the effects of capillary action of the soil and gravity. The lines are typically buried 6-8 inches below the soil surface and are spaced 12 to 18 inches apart in order to attempt to provide uniform watering to the top soil layers in-between and above the drip lines. The 12 to 18 inch spacing requirement for these buried drip lines translates into substantial installation labor costs (approximately 3 to 4 times the cost of conventional sprinkler installations). Even with the close spacing, the effects of gravity combined with the capillarity of the soil below the drip lines causes more than 50 percent of the water to be dropped below the drip line level and lost to the lawn and shallow rooted plantings due to percolation. In addition to inefficiencies, these buried lines and emission devices are plagued with problems of plant roots growing into them and plugging the emitters. State of the art solutions to this problem have consisted of using toxic chemicals impregnated within the lines or emission devices or injected into the treatment water to kill the roots around the emission device. Even if roots are kept out through chemical treatments, soil working into the emission devices is a problem because of the low velocity and mass flow rate of the water exiting the emission device (the water typically drips out).
The low flow rate emission points can also easily be plugged by insects, insect eggs and various other natural blocking agents. Finally, the large number of lines with subsurface drip irrigation make it more susceptible to mechanical damage from digging activity, planting and typical intrusive lawn use activities (i.e. installing sewers, posts, electrical lines, cable lines, etc.).
Other forms of irrigation include excavated impermeable layers located somewhere within the root zone to create moisture reservoirs for the roots to grow into. These forms of irrigation, however, require great amounts of site preparation, excavation, and back filling in order to achieve the desired results.
Another form of irrigation developed by the inventor herein is a form of irrigation in which discrete, controlled amounts of water are distributed above the thatch layer of the soil at such a rate as to create distribution caused by exceeding of the local hydraulic loading gradient and wicking action of the thatch. This form of turf irrigation is found to be more efficient than the other forms listed but still is subject to variables such as amount of thatch and turf surface irregularities.
All of the systems previously described, except for the surface drip irrigation, require extensive digging and excavation of the soil into which the irrigation system is to be installed, m driving up costs of the system dramatically. In fact, for a typical sprinkler installation, the hardware is typically only about 25% of the cost of the final installed system, the majority of costs being attributed to labor required to move earth during the installation.
To the knowledge of the inventor, no prior system for irrigating turf provides both efficient irrigation and low cost installation.